Ringed by 3.5km of scarlet citadel walls at the very heart of Běijīng, the Unesco-listed Forbidden City is China's largest and best-preserved collection of ancient buildings, and the largest palace complex in the world. Steeped in stultifying ritual and Byzantine regal protocol, this other-worldly palace was the reclusive home to two dynasties of imperial rule, sharing 900-plus buildings with a retinue of eunuchs, servants and concubines, until the Republic overthrew the last Qing emperor in 1911.